Lens cortex is unique in that it contains two major phenylalanine transfer RNAs. One of these tRNAs is specifically induced during cell differentiation and appears to be the product of a different phe-tRNA gene. Another tRNA, lys-tRNA2 is specifically inhibited during lens cell differentiation. It is the aim of this work to determine what effects these changes in the tRNA population have on the synthesis of the major structural proteins of the lens. This will be studieD in an in vitro protein synthesizing system derived from cultured lens epithelial cells using isolated mRNA for alpha crystallin.